It is widely practiced that a test subject, such as a food or a pharmaceutical product, is irradiated with X-rays, and inspected for presence or absence of a foreign matter in the subject from a transmitted X-ray image thereof. An X-ray detection device that includes a line sensor for detecting a transmission image by X-rays emitted from an X-ray source toward the subject is used for the inspection. The X-ray detection device adopts, for example, a configuration where two line sensors are arranged in parallel in such a way as to detect X-rays in different energy ranges, in a case where foreign matters to be detected are different (for example, whether the foreign matter is a piece of bone or metal included in meat). In a case of obtaining a subtraction image from X-ray images through the two line sensors, it is preferable to reduce the interval between the line sensors in order to obtain a clearer image. Accordingly, for example, it has been proposed to form two line sensors in parallel on a common sensor substrate and reduce the interval (dead-zone region) between the two line sensors (for example, see FIG. 3 in Patent Literature 1).